The present invention relates to a suspension system for an appliance, in particular, a method and apparatus to improve motion damping on a hung suspension system. The invention is particularly advantageous when used in an automatic washer.
A tub suspension system of the present invention includes a compact, easily assembled and reliable spring-mass-dampener system for suspending a floating base, on which a rotatable basket or clothes container of a clothes washing machine is mounted, supported from a cabinet in a manner to prevent vibration transference to the cabinet during normal operation of the machine and particularly as the basket is rapidly rotated during an extracting or centrifuging operation. Such a suspension system is disclosed in U.S. Pat. No. 3,744,746 to Weir et al., in U.S. Pat. No. 4,625,529 to Anderson and also in co-pending application Ser. No. 532,315.
The suspension system has a plurality of angularly spaced apart suspension assemblies interconnecting the tub floating base to the cabinet. Each of the assemblies comprises a rod with one end of each rod being resiliently connected by a coiled spring to the floating base. The coiled spring surrounds each hanger rod below the base, and transfers the weight of the base and components supported therefrom to the rod. Relative sliding movement of each rods in an axial direction is retarded or dampened by friction bushings, in this case a lower suspension ball or "collet" fitted over the rods above the spring and under the base, thereby to complete the spring-mass-dampener system.
The elimination of excessive vibrations in automatic washing, rinsing and drying machines for home use has been an area of continuing development. Excessive vibrations usually occur where there is a non-uniform distribution of clothes in a rotating clothes container or basket as the same spins rapidly to centrifuge excess water from the clothes. While a high rate of spin is desirable during the centrifuging operation, the maximum rate of spin is limited by the capabilities of the tub suspension system to isolate the machine cabinet from the vibrations or oscillatory motion caused by the unbalanced load. A complex suspension system may permit a high rate of spin, however, in order to maintain the cost of the laundry appliance within the reach of most consumers, the suspension system should also be compact, inexpensive and easily assembled.
Most state of the art hung suspension systems use a lower suspension ball that is partially split in half allowing it to grip the suspension rod at the ball's top end only. This system uses a lubricant (grease) between the rod and ball surfaces. The lubricant reduces ball wear and frictional noise. Therefore, frictional damping is limited by the small contact area of the ball to rod and the lubricant.